1. Field of the Invention
The present invention relates to a thin film magnetic head incorporating both a magnetic read head section and a magnetic write head section, a head gimbals assembly, a head arm assembly, and a magnetic disk device.
2. Description of the Related Art
For recording and reading of magnetic information (hereinafter, simply referred to as information), a magnetic disk device has been used. The magnetic disk device is configured to include, in a chassis, a magnetic disk and a thin film magnetic head, for example. The magnetic disk is the one for storage of information, and the thin film magnetic head is for recording of information onto the magnetic disk, and for reproduction of the information recorded on the magnetic disk. The magnetic disk is supported by the rotation shaft of a spindle motor, and is so configured as to rotate about the shaft. The spindle motor is being fixed to the chassis. On the other hand, the thin film magnetic head is formed on one side surface of a magnetic head slider provided at one end of a suspension. Such a thin film magnetic head is configured to include a magnetic write element and a magnetic read element, each having an air bearing surface (ABS; Air Bearing Surface) opposing the magnetic disk. Specifically for the magnetic read element, an MR element having the magnetoresistive (MR: Magnetoresistive) effects has been popularly used. The other end of the suspension is attached to the tip end of an arm supported to a fixed shaft to be able to freely rotate. The fixed shaft is the one provided upright in the chassis.
In the thin film magnetic head, the ABSs are both being in contact with the surface of the magnetic disk with a slight pressure by the biasing force of the suspension when the magnetic disk device is not in operation, i.e., when the magnetic disk is not rotating and is not in motion. In such a state, when the magnetic disk device is put in motion, and when the magnetic disk is started to rotate, the magnetic head slider is responsively moved upward slightly, thereby forming a very small spacing (magnetic spacing) between the ABSs and the surface of the magnetic disk. Stabilizing the amount of such an upward movement of the magnetic disk may lead to the recording and reproduction of information with a good accuracy.
The concern here is that, in recent years, the magnetic disk has been increased in recording density (increased in capacity), and in accordance with such an increase, the recording track has been reduced in width. With a narrower recording track as such, the thin film magnetic head is also reduced in dimension, thereby reducing not only the capabilities of a magnetic write element in terms of signal recording onto the magnetic disk but also the intensity of a signal magnetic field from the magnetic disk. In order to compensate such capability reductions, there has been a need for reducing more the magnetic spacing (for bringing closer the ABSs of the thin film magnetic head to the surface of the magnetic disk).
For meeting such a need, an attempt has been made not to move upward that much the magnetic head slider in its entirety. However, this attempt has failed in not providing enough control, and as a result, the thin film magnetic head comes in contact with very small protrusions or others on the surface of the magnetic disk. This thus causes problems including generation of abnormal signals due to heat generation, and abrasion of the thin film magnetic head itself, for example.
In order to solve such problems, the applimayt of this patent application has proposed before a thin film magnetic head provided with heat generation means on the side opposite to the ABS of a magnetic conversion element being a combination of a magnetic write element and a magnetic read element (refer to Japanese Unexamined Patent Publication No. 2003-168274). With such a thin film magnetic head, during driving of the magnetic disk device, the magnetic conversion element is protruded to the side of the ABS utilizing the thermal expansion of the area in the vicinity of a heating element due to the heat generation thereof, thereby aiming to reduce the magnetic spacing. At this time, the amount of protrusion is adjusted with a high precision through control over the amount of heat generation so that the magnetic spacing reduced as such may be remained very small with a good stability. This accordingly leads to the great reduction of a probability of contact between the surface of the magnetic disk and the thin film magnetic head.
After the disclosure of such a thin film magnetic head, another type of thin film magnetic head is proposed in which a temperature detection section is provided, and based on information about the detected temperature, the amount of power supply for a heating element is controlled (an example includes Japanese Unexamined Patent Publication No. 2003-272335). In such a thin film magnetic head, a pair of heating elements are so provided as to sandwich therebetween a magnetic conversion element along the rotation direction of a magnetic disk, and the temperature detection section is provided between one of the heating elements and the magnetic conversion element. Moreover, as a related art, described is a magnetic disk device including a magnetic head slider provided with a heating element, and an arm provided with a temperature sensor (an example includes Specification of U.S. Pat. No. 5,991,113). Also in Japanese Unexamined Patent Publication No. 2008-165950, described is a magnetic head slider including two heaters in any same hierarchy in the vicinity of a thin film magnetic head. Still also in Japanese Unexamined Patent Publication No. 2007-280502, described is a magnetic head slider including a heater in the vicinity of a read element.
In spite thereof, because the magnetic disk has been recently increased in recording density (increased in capacity) all the more, the demand is increasingly growing for the magnetic spacing much smaller in size with much better stability to meet such an increase of recording density. With the thin film magnetic head in Japanese Unexamined Patent Publication No. 2003-168274, however, there is a problem of difficulty in controlling an extremely small magnetic spacing with a high precision through control over the power application to the heating element. This is because the temperature of the area in the vicinity of the heating element is easily affected by any heat generation due to driving of the magnetic conversion element in use, by the temperature environments in the vicinity area, and others. Similarly, with the thin film magnetic head in Japanese Unexamined Patent Publication No. 2003-272335, due to the configuration that the heating elements are so provided as to sandwich therebetween the magnetic conversion element along the rotation direction of the magnetic disk, the displacement in response to any change of power application may not be enough in the direction orthogonal to the ABS. As a result, the heat generation of the heating elements may possibly increase also the temperature of the magnetic conversion element. Also similarly, with the magnetic disk device in the Specification of U.S. Pat. No. 5,991,113, the distance is large between the heating element and the magnetic conversion element, and this thus may result in a large time lag until the amount of protrusion shows a change after the change of power application. Also similarly, with the magnetic head slider in Japanese Unexamined Patent Publication No. 2008-165950 and that in Japanese Unexamined Patent Publication No. 2007-280502, a certain degree of control may be indeed possible over the distance between the read element and the surface of the magnetic disk, but a sufficient degree of control may be difficult over the distance between a write element and the surface of the magnetic disk.
In consideration thereof, the ABS is expected to be controlled by the amount of protrusion thereof with a higher precision to ensure that the magnetic spacing is to be very small with a high precision.